Diagnostic method and system for detecting early age macular degeneration, maculopathies and cystoid macular edema post cataract surgery

A retinoscopic device, technique and scale for estimating the reflectance of the macula pigment optical density (MPOD) in normal and abnormal eyes in order to detect early pathology of the retinal pigment epithelium and photoreceptors thus screening for macular pathology the most prevalent of which is Age-related Macular Degeneration (AMD) and retinal edema and cystoid macular edema post cataract surgery.

FIELD OF THE INVENTION

This invention relates to a method and system for using a calibrated retinoscope and parallel light technique to estimate the reflection of melanin particles in the retina to detect macular degeneration prior to physical symptoms.

BACKGROUND OF THE INVENTION

In the Western world, maculopathy or AMD is the leading cause of blindness in the elderly population and affects 10%-13% of adults over 65 in North America, Europe, Australia and Asia In 2012 the undiagnosed prevalence of AMD in the USA was estimated to be 2.3 million. Estimates of the global cost due to AMD are US$343 billion with US$255 billion in direct health care costs.

According to the International Classification age-related maculopathy (ARM) is a degenerative disease of the macula characterized in the early stage by large, soft yellow drusens, hyper-/hypopigmentation of the retinal pigment epithelium (RPE), and a moderate loss of central vision (age-related maculopathy). Age related maculopathy disease (AMD) is a late stage of ARM. Dry AMD refers to geographic atrophy and wet AMD is characterized by choroidal neovascularization (CNV), detachment of the RPE, subretinal hemorrhage or retinal scarring.

Currently, several AMD classification schemes, grading systems, and severity scales have been developed in an effort to provide standards to assist clinicians and researchers in the diagnosis and management of this important disorder. The most current clinical classification of AMD takes in consideration pigment abnormalities and is illustrated inFIG. 16.

It is believed the ultimate therapy for AMD will lie in the preclinical identification of those who are genetically “at risk” for the disease and treatment with genetically specific supplements. At the present time, AMD is initially diagnosed by an ophthalmologist or optometrist with a fundus examination and Amsler grid of patients who complain of a decrease in their vision. The hallmarks of early AMD are yellow drusens and pigment abnormalities (hypo and hyperpigmentation) of the retinal pigment epithelium (RPE) which occur after the onset of the AMD process. AMD is characterized by a degeneration of the retinal pigment epithelium and photoreceptors (rod and cones) and a thickening of the Bruch's membrane in the macula.

The early detection of AMR could reduce the growing societal burden by targeting and emphasizing modifiable habits earlier in life. With genetic testing antioxidants and other supplements specific to the patient's genotype can be recommended. More frequent examinations of those at high risk due to family history or signs of early or intermediate disease would be beneficial.

It is believed that the pigmentary changes observed in the macula of AMD eyes are attributable to degenerative changes in the highly melanized RPE cells because most of the early clinical signs and histopathological changes have been localized to this cell layer. It has been suggested that melanin in the retinal pigment epithelium (RPE) and choroid may protect the macular region by its antioxidant capability and its capability to attenuate or reflect light thereby decreasing photochemical light damage.

In retinoscopy, a light is shone into a patient's eye and the reflected “streak” of light is used to estimate the correction of a patient's refractive error. The results are then the beginning point for a refraction. However, with the calibrated retinoscope and this technique, the brightness of the reflected beam is dependent on the health of the pigment epithelium and thus gives an early indication of macular pathology. This calibrated diagnostic retinoscope and technique allow the general ophthalmic physician to detect early and late stages of the destruction of the retinal pigment epithelium in AMD. The common denominator between AMD and the pupillary reflex in retinoscopy lies in the melanin pigment particles of the microvilli of the retinal pigment epithelium (RPE) which surrounds the photoreceptors, the choroid and/or the outer segment of the cones.

In 1926, Jacob C Copeland designed a retinoscope (U.S. Pat. No. 3,597,051) and a technique of retinoscopy which has since been taught to optometrists and ophthalmologists for obtaining an objective measurement of the refractive error of patient's eyes for spectacles and/or contact lenses. All retinoscopes have been based upon on his work.

Originally, Copeland's and other retinoscopes used diverging light and spots of light to estimate the refractive error. Copeland introduced streak retinoscopy in the US and it was rapidly accepted because it made determination of the axis of astigmatism more precise. The technique was referred to as “streak retinoscopy” because a streak of reflected light, or the pupillary reflex, was produced during the technique.

In 1968, Copeland and Walter M. Lewis designed the Copeland Optec 360 Streak Retinoscope, U.S. Pat. No. 3,597,051 (as illustrated inFIG. 17). This retinoscope contains a +20.00 D condensing lens and a bi-pin filament bulb. When the thumb-slide is in its upper position, the filament of the lamp is less than five centimeters from the condensing lens and the rays emanating from the filament and passing out of the condensing lens are diverging. Moving the thumb-slide to a lower position causes the light rays to converge. When the filament is at the focal point of the +20.00 D lens or approximately 5 cm from the +20.00 D lens, the light rays are parallel.

Sims' calibrated refractive retinoscopic techniques uses converging rather than diverging light. The Sims' retinoscope can also be used for calibrated diverging or conventional diverging retinoscopic techniques. It has been modified so that auxiliary lenses can be attached to the back of the head of the retinoscope to place the examiner's eye in focus with the patient's pupillary plane in order to have an identical (conjugate) image of the pupillary reflex. Parallel light is used after the refractive error has been determined to judge the streak on a reflectance scale 1 (very poor and difuse) to 5 (brilliant).

In conventional retinoscopy, the pupillary reflex cannot be used to evaluate the melanin reflectance. The endpoint of conventional retinoscopy is an infinity neutrality reflex which fills the pupil and there is no streak. The width of the reflected retinoscopic light from the reflecting membrane spans an area much larger than the size of the pupil and is enormous, making it impossible to evaluate the reflectance of the macular pigment (MP). With conventional retinoscopy, the refractive error is initially determined by under correcting the refractive error to create a visible with-motion pupillary streak reflex that expands and moves at an exponentially increasing speed as neutrality is reached. These exponential changes of the with-motion streak makes it impossible to evaluate the reflectance of the MP.

Production of the Pupillary Reflex:

The cones act as an optical waveguide for visible light due to their tubular structure and the index gradient between the cell wall and internal medium. Since the cone's receptors are tightly packed, they act as a “fiber optic plate” extending from the external limiting membrane to the pigment epithelium (as illustrated inFIG. 18). Therefore light, that strikes the outer limiting membrane located at the openings of the photoreceptors, is transmitted to the photosensitive pigment in the outer segments by a waveguide mechanism and then reflected to the outer limiting membrane.

The reflected light from the retina pigment epithelium (RPE) interface appears to be due to Fresnel reflection from the melanin granules within the melanosomes in the RPE. A Fresnel reflection is a reflection of light on a planar interface between two homogeneous media having different refractive indices. The melanin granules in the pigment epithelium have a high index of refraction compared to the surrounding tissue. The reflected light then reenters the photoreceptors and transmitted to the external limiting membrane (ELM) and pupil. The ELM is considered the effective ocular reflecting surface for visible light in the performance of retinoscopy or photorefraction. Conventionally, the pupillary reflex is used to measure or estimate a refractive error, not to evaluate the reflectance from the melanin pigment.

Macular Degeneration and Reflectance:

Most of the early clinical signs and histopathological changes have been localized to the pigment epithelium. It is believed that it is the melanin in the retinal pigment epithelium (RPE) and choroid which protects the macular region through its antioxidant capability and its capability to attenuate blur light thereby decreasing photochemical light damage. Healthy pigment epithelium is more reflective than that which is damaged and when evaluated produces a brilliant to clear streak.

The calibrated retinoscope and diagnostic technique described in this patent application allows the average ophthalmic physician to detect early and late stages of the destruction of the retinal pigment epithelium in AMD.

The relevant prior art includes the following references:

SUMMARY OF THE INVENTION

The primary object of the present invention is to improve the detection of age-related maculopathies (ARM & AMD) other maculopathies and cystoid macular edema post cataract surgery using a modified retinoscope.

An additional object of the present invention is to provide a retinoscope capable of performing several calibrated refractive and diagnostic retinoscopic techniques and conventional retinoscopy.

The present invention fulfills the above and other objects by providing a retinoscopic device, technique and scale for estimating the reflectance of the macula pigment optical density (MPOD) in normal and abnormal eyes in order to detect early pathology of the retinal pigment epithelium and photoreceptors thus screening for macular pathology, the most prevalent of which is Age-related Macular Degeneration (AMD).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIG. 1, a side partial cutaway view of a retinoscope1having a thumb-slide2and a condensing lens3and a lamp4is shown. The lamp4includes a linear filament5designed to create a “streak” image which is reflected from a patient's retina and seen by a practitioner, such as an optometrist or ophthalmologist. The thumb-slide2moves the power capsule housing the lamp4moves up and down along a handle of the retinoscope6so that when the thumb-slide2is in a maximal upward position, the filament5is less than 5 cm from lens3which has an approximate power of +20.00 D. When the thumb-slide2is in a maximal down position, the filament5is approximately 6.6 cm from the lamp4. The practitioner can view the light rays reflected from the patient's retina through a small openings7in mirror8and head of retinoscope. The examiner can only see the retinoscopic light on the patient's iris and the reflected pupillary reflex. The examiner nevertheless is able to move the pupillary reflex toward neutralization by the movement and orientation of the pupillary reflex. The examiner draws all of the retinoscopic signals from the pupillary reflex, that is, when to change or rotate the retinoscopic streak to achieve neutralization of the spherical and cylindrical error.

With reference toFIG. 2, calibration of the retinoscope requires a calibration line11in the knurl area9on the power capsule10to align the Plates7A and7B for converging infinity retinoscopy and Plates7C and7D for diverging retinoscopy after the retinoscope is calibrated to the specifications in the Calibration Chart18.

With reference toFIG. 3, a schematic view of light rays12emanating from a retinoscope1in a diverging pattern13is shown. In diverging retinoscopy the lamp4is within the focal length of lens3. The proximity of the lamp4to the lens3causes the light rays12emitted from the retinoscope1to spread out into a diverging pattern13. The retinoscopic technique of identifying and neutralizing a refractive error is the same with calibrated diverging retinoscopy as with conventional retinoscopy. Calibrated diverging retinoscopy differs from conventional retinoscopy in that the divergence of the emitted retinoscopic light rays12is calibrated to a fogging lens whose focal length is equal to one's retinoscopic working distance. The endpoint of calibrated diverging retinoscopy can be an infinity retinoscopic endpoint which is identical to the endpoint of conventional retinoscopy or a +0.50 D with-motion pupillary reflex.

With reference toFIG. 4, a schematic view of light rays12emanating from a retinoscope1in a converging pattern14is shown. In converging retinoscopy, the lamp4is displaced beyond the focal length of lens3. The increased distance of the lamp4from the lens3causes the light rays12emitted from the retinoscope1to focus into a converging pattern14.

With reference toFIG. 5, a flow chart showing the steps for measuring a retinoscopic working distance for use in calibrating a retinoscope for converging and diverging retinoscopy is shown. The examiner's retinoscopic working distance is optically measured by focusing the retinoscopic light into an emmetropic eye using the thumb slide until a neutrality reflex occurs15. Then, the retinoscopist holds the thumb-slide on the retinoscope in place and the emitted retinoscopic light is focused onto a wall by moving the retinoscope towards the wall until the streak is in focus16. Finally, the distance between the wall and retinoscope is measured to obtain the examiner's retinoscopic working distance17.

With reference toFIG. 6, a calibration chart18is shown. The calibration chart18lists the retinoscopic working distance in centimeters19and the required power of the calibration lens to be held in front of the retinoscope, which is displaced from a wall a distance equal to the examiner's retinoscopic working distance19, in order to calibrated the diverging retinoscopic light for an infinity endpoint20and a +0.50 D endpoint21. Chart18also lists the distance a retinoscope must be held from a wall to calibrated the retinoscope using converging light for a +0.50 D endpoint22and a +0.75 D endpoint23, when performing retinoscopy from one's retinoscopic working distance.

With reference toFIG. 7-A, an attachable plate24for retrofitting a retinoscope1when calibrated for a +0.50 D with-motion endpoint pupillary reflex using converging rays14emitted from the retinoscope1is shown. The plate24shown here is a +0.50 D converging plate25and is used when the converging light emanating from the retinoscopies is calibrated for a +0.50 D with-motion retinoscopic endpoint, as shown further inFIG. 8. The +0.50 D converging plate25has a front surface26, a rear surface27and an alignment line28. The plate24is attachable to the retinoscope via an attachment means29, such as screws nuts, etc. The plate24is moveable via an adjustment means30, such as a slot that moves along a screw, so that a user may adjust the alignment line28up or down to be in alignment with the calibration line11on the power capsule10. After the retinoscope is calibrated and plate24secured into position, the alignment line28on plate24allows the retinoscopist to know where to place the calibration line11on the power capsule10to obtain a +0.50 D retinoscopic endpoint using converging light, as shown further inFIG. 8-A.

With reference toFIG. 7-B, an attachable plate24for retrofitting a retinoscope1when calibrated for a +0.75 D with-motion retinoscopic reflex using converging light rays14emitted from the retinoscope1is shown. The plate24shown here is a +0.75 D converging plate31and is used when the converging light14emanating from the retinoscope is calibrated for a +0.75 D with-motion retinoscopic endpoint, as shown further inFIG. 9. The +0.75 D converging plate31has a front surface26, a rear surface27and an alignment line28. The plate24is attachable to the retinoscope via an attachment means29, such as screws nuts, etc. The plate24is moveable via an adjustment means30, such as a slot that moves along a screw, so that a user may adjust the alignment line28up or down to be in level with the calibration line11on the power capsule10. After the retinoscope is calibrated and plate24secured into position, the alignment line28on plate31allows the retinoscopist to know where to place the calibration line11on the power capsule10to obtain a +0.75 D retinoscopic endpoint using converging light, as shown further inFIG. 9-A.

With reference toFIG. 7-C, an attachable plate24for retrofitting a retinoscope1when calibrated for an infinity endpoint using diverging light rays13emitted from the retinoscope1is shown. The plate24shown here is an infinity endpoint diverging plate32and is used when the diverging light13emitted from the retinoscope is calibrated for an infinity retinoscopic endpoint, as shown further inFIG. 10. The infinity diverging plate32has a front surface26, a rear surface27and an alignment line28. The plate24is attachable to the retinoscope via an attachment means29such as screws, adhesive, nuts, etc. The plate24is moveable via an adjustment means30, such as a slot that moves along a screw, so that a user may adjust the alignment line28up or down to be level with the calibration line11on the power capsule10after the retinoscope is calibrated. After the retinoscope is calibrated and plate32secured into position, the alignment line28on plate32allows the retinoscopist to know where to place the calibration line11on the power capsule10to perform retinoscopy with diverging light rays to obtain an infinity retinoscopic endpoint adjusted to one retinoscopic working distance as shown further inFIG. 10-A.

With reference toFIG. 7-D, an attachable plate24for retrofitting a retinoscope1when calibrated to a +0.50 D with-motion pupillary reflex endpoint using diverging retinoscopic light rays13is shown. The plate24shown here is a diverging plate33and is used when the diverging light emanating from the retinoscope is calibrated for a +0.50 D with motion retinoscopic endpoint as shown further inFIG. 11. The +0.50 D diverging plate33has a front surface26, a rear surface27and an alignment line28. The plate24is attachable to the retinoscope via an attachment means29, such as screws, adhesive, nuts, etc. The plate24is moveable via an adjustment means30, such as a slot that moves along a screw, so that a user may adjust the alignment line28up or down to be in alignment with the calibration line11on the power capsule10after the retinoscope is calibrated. The alignment line28on plate33allows the retinoscopist to know where to place the calibration line11on the power capsule10to perform retinoscopy with diverging light rays to obtain a +0.50 D retinoscopic endpoint adjusted to one retinoscopic working distance as shown further inFIG. 11-A.

With reference toFIG. 8, a flow chart showing the steps for calibrating a retinoscope for a +0.50 D with-motions retinoscopic endpoint using converging retinoscope light rays14is show. First, the retinoscopic working distance is optically measured34as shown inFIG. 5. Then, the required focal length of the emitted retinoscope light for a +0.50 D retinoscopic endpoint is determined35using the calibration chart18illustrated inFIG. 6. For example, if the retinoscopic working distance is 67 cm, the required focal length of the emitted retinoscopic light is 100 cm. Next, the retinoscope is placed at the proper focal length from a wall36and focused37. Finally38, the alignment line28on the +0.50 D converging plate25is aligned with the calibration line11on the power capsule10as shown further inFIG. 8-Aand secured39.

With reference toFIG. 8-A, a retinoscope1having a +0.50 D converging plate25attached thereto is shown. The retinoscope1has been calibrated for a +0.50 D pupillary reflex endpoint using converging retinoscope light rays14. The technique for performing retinoscope using a retinoscope calibrated for a +0.50 D retinoscopic endpoint is the same as in conventional retinoscopy, except that the calibration line11on the power capsule10is aligned with the alignment line28on the +050 D converging plate25and the retinoscopic endpoint is a +0.50 D with-motion retinoscopic reflex with the +0.50 D pupillary reflex and intercept moving in unison.

With reference toFIG. 9, a flow chart showing the steps for calibrating a retinoscope for a +0.75 D with-motions retinoscopic endpoint using converging retinoscope light rays14is show. First, the retinoscopic working distance is measured34as shown inFIG. 5. Then, the required focal length of the emitted retinoscope light is determined35using the calibration chart18illustrated inFIG. 6. For example, if the retinoscopic working distance is 67 cm, the required focal length of the emitted retinoscopic light is 133 cm. Next, the retinoscope is placed at the proper focal length from a wall36and focused37and the thumb-slide held in position. Finally38, the alignment line28on the +0.75 D converging plate31is aligned with the calibration line11on the power capsule10of retinoscope1as shown further inFIG. 8-Aand secured40.

With reference toFIG. 9-A, a retinoscope1having a +0.75 D converging plate31attached thereto is shown. The retinoscope1has been calibrated for a +0.75 D endpoint using converging retinoscopic light rays14. The technique for performing retinoscopy using a retinoscope calibrated for a +0.75 D retinoscopic endpoint is the same as in conventional retinoscopy, except the calibration line11on power capsule10is aligned with the alignment line28on the +075 D converging plate31and the retinoscopic endpoint is a +0.75 D retinoscopic and moves in unison with the intercept.

With reference toFIG. 10, a flow chart showing the steps for calibrating a retinoscope1for an infinity retinoscopic endpoint using diverging retinoscopic rays13is shown. First, the retinoscopic working distance34is measured in centimeters, as shown inFIG. 5. Next41, the retinoscopic working distance in centimeters19is matched to the power of the calibration lens required20using the calibration chart18. For example, if the retinoscopic working distance is 67 cm, the power of calibration sphere would be +3.00 D. Next, the retinoscope1is placed at a distance from the wall equal to the retinoscopic working distance42. Next, the +3.00 D calibration sphere as determined from41is placed in front of the retinoscope43. With the thumb-slide2in the maximal upward position and the diverging retinoscopic light shinning through the +3.00 D calibration spherical lens, the thumb-slide2is lowered until the retinoscopic streak is focused onto the wall37. If the retinoscopic streak fails to focus onto the wall, the bulb4is advanced towards the condensing lens3within the retinoscope1and the procedure repeated until the retinoscopic streak is focused onto the wall,44. Next45, the alignment line28on the infinity diverging plate32is aligned with the calibration line11on the power capsule10and secured in position46as shown further inFIG. 10-A.

With reference toFIG. 10-A, a retinoscope1having a diverging plate32attached thereto is shown. The retinoscope1has been calibrated for an infinity retinoscopic endpoint using diverging retinoscope light rays13. The technique for performing retinoscopy using an infinity retinoscopic endpoint with the emitted retinoscopic light rays calibrated to the examiner's retinoscopic working distance is the same as in conventional retinoscopy, except that the calibration line11on the power capsule10is aligned with the measuring line28on the infinity plate32.

With reference toFIG. 11, a flow chart showing the steps for calibrating a retinoscope1for a +0.50 D retinoscopic endpoint using diverging retinoscope light rays13is show. First the working distance is measure centimeters34, as shown inFIG. 5. Next41, the retinoscopic working distance in centimeters19is matched to the power of the calibration lens required21using the calibration chart18. For example, if the retinoscopic working distance is 67 cm the power of the calibration sphere would be +3.50 D. Next, the retinoscope1is placed at a distance from the wall equal to the retinoscopic working distance42. Next, the +3.50 D sphere is placed in front of the retinoscope43. With the thumb-slide2in the maximal upward position and the diverging retinoscopic light shinning through the +3.50 D calibration lens, the thumb-slide2is lowered until the retinoscopic streak is focused onto the wall37. If the retinoscopic streak fails to focus onto the wall, the bulb4is displaced toward the +20 D condensing lens3within the retinoscope and the procedure repeated until the retinoscopic streak is focused onto the wall,44. Next47, the alignment line28on +0.50 D diverging plate33is aligned with the calibration line11on the power capsule10and secured in position48as shown further inFIG. 11-A.

With reference toFIG. 11-A, a retinoscope1having a +0.50 D diverging plate33attached thereto is shown. The retinoscope1has been calibrated for a +0.50 D retinoscopic endpoint using diverging light rays13exiting the retinoscope. The technique for performing retinoscopy using a retinoscope calibrated to one's retinoscopic working distance for a +0.50 D retinoscopic endpoint is the same as conventional retinoscopy except the retinoscopic endpoint is a +0.50 D with-motion retinoscopic endpoint and the calibration line11is aligned with the alignment line28. In contrast to the +0.50 D retinoscopic endpoint produced with converging rays emitted from the retinoscope inFIG. 8-A, with diverging rays the +0.50 D retinoscopic endpoint moves faster than the intercept.

With reference toFIG. 12, a flow chart showing the steps for performing a calibration check on retinoscopes calibrated to emit converging rays14as shown inFIGS. 8-Aand9-A is shown. First, the practitioner assumes his or her routine retinoscope distance49. Then the practitioner lowers the thumb-slide2of the retinoscope from its maximal upward position until a neutrality reflex is seen in an emmetropic eye12and holds the thumb-slide in this position15. If the calibration line11on the power capsule10is level with the alignment line28on the converging plates25or31, the retinoscope is calibrated50. In the Copeland Optec 360 Streak Retinoscope, the thumb-side is kept in the most superior position by a spring.

With reference toFIGS. 13 and 14, a rear view and a side view, respectively, of a retinoscope1having an upper slide bar51attached to the body of the retinoscope and located superiorly to the thumb-slide2thereto and having a lower slide bar56attached to the body of the retinoscope and located inferiorly to the thumb-slide2is shown. The slide bars51,56are attachable to the retinoscope via an attachment means29, such as screws, nut, etc. The slide bars51,56are moveable via an adjustment means30, such as a slot that moves along a post54. After the retinoscope is calibrated, the slide bars51,56are adjusted to touch the top and bottom, respectively, of the thumb-slide2and locked in place via a locking means55, such as a screw, etc., to prevent the thumb-slide2from moving upward or downward.

Although a practitioner may use a +0.50 D retinoscopic endpoint or a +0.75 D retinoscopic endpoint, the +0.50 D retinoscopic endpoint is easier, faster and more convenient to confirm than the +0.75 D retinoscopic endpoint, since during retinoscopy, the neutrality reflex is displaced 2 lenses from the +0.50 D retinoscopic endpoint and 3 lenses from the +0.75 D retinoscopic endpoint.
Finally with reference toFIG. 15, a front perspective view of a bulb extender52of the present invention is shown. The bulb extender52acts as a spacer to increase the height of a lamp4and filament5within the retinoscope1. The bulb extender52elevates lamps4having shorter filaments5towards the lens3in order to increase the divergence of emitted retinscopic light. The bulb extender52has at least one aperture53to allow electronic communication between a power source of the retinoscope1and the filament5.

With reference toFIGS. 19A-22, the measurement of the reflectance of the MPOD is preferably performed with a modified Copeland Optec 360 Streak Retinoscope, with a halogen or incandescence bulb with a linear filament and an elongated permanent or attachable head rest, as illustrated inFIG. 19Aprojecting parallel light rays. The thumb-slide moves the bulb in relation to a +20.0 D spherical lens within the retinoscope to emit parallel light. The slide locks maintains the retinoscope in calibration when performing retinoscopy with diverging, converging or parallel retinoscopic light (as illustrated inFIGS. 1-15). The retinoscopic technique for detecting AMD requires the retinoscope to emit parallel light rays from the same retinoscopic working distance for each eye. The elongated head rest allows the examiner to were his or her glasses.

Formula for Calibration of Retinoscope to Emit Parallel Light:

The formula for determining the focal length and power of the pupillary image of the retinoscope emitting parallel light is:
ImageI1+ImageI3=t(D) at emmetropia
ImageI1=vergence of retinoscopic light (D
ImageI3=pupillary reflex (D)
t(D)=RWDexpressed in diopters
Since the vergence of parallel light (Image I1) is 0.00 D, the pupillary reflex is equal to the retinoscopic working distance (cm) expressed in diopters.
ImageI3=t(D) at emmetropia
Upon neutralization of the patient's refractive error and the fulfillment of the examiner's retinoscopic requirements, conjugate or identical images are formed in the patient's and an examiner's eyes.
Requirements for Examiner to See Conjugate Images of the Reflected Pupillary Streak (Image I3)1. The examiner's refractive error must be corrected.2. If the retinoscopist is presbyopic, a spherical lens with a focal length equal to the retinoscopic working distance attached to the back of the retinoscope will produce a clear image of the pupillary streak.3. The retinoscopic working distance must be the same for the right and left eyes.4. The patient's right eye must be examined by the retinoscopist's right eye and vice versa.5. The evaluation of the diagnostic pupillary streak requires an 8-10° off-axis retinoscopic position, laterally displaced. This allows the patient to fixate on the Snellen letters, reduces accommodation and maintains central fixation. An 8-10° off-axis position requires the retinoscope to be displaced 4 cm laterally to the patient's pupil for a 60-65 cm retinoscopic working distance.6. The highest concentration of pigment of located in the fovea. The foveal pigment decreases precipitously by a factor of 1/300, 7-8° from the fovea axis to the periphery of the retina (Beatty). A decrease in the 8-10° off axis reflectance of the pupillary reflex as compared to on-axis retinoscopy is more indicative of RPE damage and loss of melanin pigment of the retinal pigment epithelium.7. A 3-4 mm undilated pupil produces the optimal conjugate pupillary reflex. A dilated pupil induces higher order aberrations blurring the optical qualities of the pupillary streak. A dilated pupil will induce aberrant astigmatic error in the pupillary reflex, especially in the vertical meridian.
Calibration of Retinoscope to Emit Parallel Light Rays:1. Move the thumb-slide to focus the retinoscopic light through a spherical lens onto a wall displaced the focal length of the sphere from the wall. Adjacent slide bars51and56to keep retinoscope calibrated emitting light.2. Align the arrow head of the “parallel calibration line” Ξ symbol on the calibration plate or the attachable Ξ emblem inFIG. 21with the circumferential calibration line above the knurl to mark the position of the power capsule housing the bulb for future parallel infinity retinoscopies.4. Attach calibration plate to the side of the retinoscope, as illustrated inFIG. 21.5. Adjust the slide-bar to maintain the thumb-slide in a fixed position to maintain the calibration of the retinoscope for future diagnostic parallel and converging or diverging retinoscopies, as illustrated inFIG. 19B-E. The thumb-slide and slide bars allows one to change the vergence of the retinoscopic light from converging or diverging retinoscopy to parallel without moving the retinoscope or changing the retinoscopic working distance.

The luminance of the calibrated pupillary streak is graded on a scale of 1-5, as illustrated inFIG. 22, to evaluate the severity of the age-related maculopathy or degeneration (AMD) and other maculopathies.