“Declare the past, diagnose the present, foretell the future.”
In this section, I will deal with various diagnostic methods which are common in practice for the diagnosis of mainly Intraocular malignancies. Diagnostic modalities used for extraocular malignancies will be considered in the respective chapters.
Even though the twenty-first century has seen a boom in the diagnostic armamentarium available to the ophthalmologist, the art of good history taking can never be out of fashion.
- History of the present complaints, their duration, and associated complaints can provide multiple clues. If the duration of complaints has been seen over a long period of time with minimal change; a chronic condition can be anticipated. A sudden change in vision is an alerting sign.
- Personal history pertaining to the patient's occupation will provide us the visual needs of the concerned.
- Any previous history of other malignancies, its treatment history may provide clues with the etiology of the present condition.
- A positive family history of malignancies alerts the physician of the possibility of a familial trait.
- Patients should be encouraged to provide with history no matter how trivial it may seem.
- Enquire whether the present complaints were noticed by the patient or were diagnosed coincidently by someone else.
- Time spent in history-taking helps in the development of a good doctor-patient relationship. As stated:
It is a good habit to check the current refraction and comparing with previous spectacles. This will not only detect changes but also show a sudden hyperopic shift providing a diagnostic clue.
3.External local examination
This step is accomplished while having an interaction with the patient. Any strabismus, lid abnormalities, pigmentary changes in the ocular/peri-ocular region can be diagnosed. Examination of the regional lymph nodes is an important but often missed step.
4.Slit Lamp Biomicroscopy.[ 1],
One of the most important investigative modalities not only provides us with details about the primary tumor but also the presence of any associated anomalies and secondary effects.
- Location of tumor (be it in the anterior segment or the posterior segment)
- The extent of the primary tumor (clock minutes in a clockwise direction for the anterior segment and in clock hours for the posterior segment).
- Note the anterior and the posterior margins. The color, shape, consistency, surface, associated vascularity of the tumor should be noted.
- Anterior chamber angle should be investigated by gonioscopy in suspicious cases, also to rule out any impacted foreign body mimicking a tumor.
- Any inflammatory changes in the anterior chamber(AC) should be further investigated. Cells in AC may be actually neoplastic cells as seen in Retinoblastoma or leukemia. Cells in the anterior hyaloid may be inflammatory, old red blood cells, or neoplastic cells.
- The anterior chamber should be carefully inspected to rule out any seeding, neovascularization, corneal changes, and any secondary changes in the iris. Likewise, the conjunctiva, episclera, and sclera should be inspected carefully and any changes observed can be compared with the other eye.
- Lenticular changes are important to pay heed to. A sectoral cataract is seen in iris/ciliary body tumors. The lens may be subluxated in ciliary body pathologies. If the pre-existing cataract is present, the patient should be informed of its increase during the course of various treatment modalities.
IDO is an art perfected only with practice and patience. Once perfected it can reveal a plethora of findings.
- Both eyes should be examined even in unilateral conditions.
- The examination should be done in a systematic manner starting from the periphery to the posterior. Starting examination from the posterior pole makes patients uncomfortable especially the photophobic ones.
- A complete examination by indentation for assessing the ora should be the goal.
- Any mass lesion should be examined in terms of its anterior and posterior extent, surface, color, margins, vascularity.
- Secondary changes like RPE changes over the leison generally show chronicity. RPE changes around a lesion should also be noted. The presence of drusens, the orange pigment should be looked for.
- Particular note should be made of any lesion in relation to optic nerve head and fovea.
- Associated features like hemorrhages, exudates should be noted. In any case of associated retinal detachment; etiology of rhegmatogenous or exudative nature should be found. Examination in a sitting and supine position often clears the air.
- IDO is especially valuable when assessing peripheral lesions like peripheral vascular lesions, varix of ampulla which can mimic a tumor.
- A 20D lens is estimated to have a field diameter of 12 mm. Any lesion can be roughly measured in this relation. A lesion filling half or full of the 20D field will approximately measure 6mm or 12mm.
1.B scan Ultrasound:
B-scan ultrasound should ideally be done by the treating ocular oncologist.
- It not only confirms the clinical diagnosis but also rules out mimicking pathologies.
- USG is used for determining the extent, dimensions of the mass lesion.
- Its use is not only limited during diagnosis but also after treatment in assessing the response.
B scan features in Choroidal Melanoma( useful only when the lesion is greater than 1 mm). The various features on the B scan are due to the homogenous nature of melanoma cells with minimal fibrous tissue.
- Low internal reflectivity
- An acoustic quiet area at the base of the tumor is called acoustic hollowness.
- Choroidal excavation
- Orbital shadowing: the reflectivity posterior to the tumour is low.
- On A scan low to medium reflectivity is seen with characteristic "positive angle kappa": the reflectivity decreases after a high spike.
- Tumor diameter and thickness on B scan are the basis of a treatment plan. B scan post-treatment judges the activity on the basis of thickness and clinical characteristics.
- B scan is also used in judging the placement of a plaque.
- B scan is also helpful in judging extra ocular spread.
- In retinoblastoma presence of calcification with characteristics back shadowing is helpful in the diagnosis. Although B scan can help in detecting extraocular spread, MRI is a better diagnostic modality for the same.
- In cases of choroidal metastasis which has medium to high reflectivity shows a characteristic negative kappa angle sign.
- Choroidal osteoma has a high reflectivity with shadowing posterior to it.
- B scan is complementary to any diagnostic aids. It is not a basis for diagnosis
2.Ultrasound Biomicroscopy ( UBM)
- Useful modality in lesions involving the iris and ciliary body.
- Its use in detecting anterior chamber spread and staging in advanced retinoblastoma can be a useful aid in treating such patients.[ 4]
- Especially useful in ciliary body melanoma, ring melanoma, diffuse xanthogranuloma.
3 Fundus Imaging ( with WIDE FIELD IMAGING)[ 5,6,]
- Essential in follow-up of suspicious lesions.
- Monitoring treatment in assessing response and detecting any recurrence at the earliest.
- Used as a tool for patient education.
Standard Fundus Photograph
- Captures 30-35 degrees of the fundus.
- Useful for lesions located in the posterior pole
- Peripheral images can be captured but require skill.
- 120 degrees of the fundus can be achieved.
- The imaging modality of choice in Retinoblastoma where excellent images can be captured.
- The use of indentation can provide images of the ora.
- Utilizes a contact handheld camera with a coaxial light source.
- Has multiple different lenses which can be used to capture images of the anterior segment.
- Fundus angiography is an added benefit.
- Needs clear media, hence its use has been restricted to the pediatric cohort.
- Use of corneal contact with simultaneous scleral illumination
- Since it utilizes transscleral illumination , issues of glare are less
- Images obtained are of high quality with true color reproduction.
- Can be used in small pupil and cataract
- This machine has not been in production since 2012.
- Use of confocal scanning laser imaging
- Ultrawide field imaging is obtained with approximately 200 degrees of fundus
- Provision of having wide field autofluorescence and angiography from the same machine
- Images are reproduced in shades of green and red, and that is its major disadvantage.
4. Fundus Autofluorescence (FAF)
- Works on the principle of detection of natural emission from fluorophores inside the eye namely lipofuschin and melanin.
- FAF is an excellent modality in viewing abnormalities of the RPE.
- Subtle subretinal fluid and its legacy can be well appreciated by FAF
- Hyper autofluorescence secondary to orange lipofuschin is very suggestive of a malignancy, although it can also be seen in benign lesions.
- Typical 'comet tail' and 'hourglass ' changes secondary to resolved subretinal fluid are better appreciated by FAF
- Recent subretinal fluid is generally hyper autofluorescent whereas old fluid is hypo autofluorescent.
5. Optical Coherence Tomography ( OCT & EDI OCT )
- Newer generation OCT with high-resolution images retina at microscopic detail.
- OCT is generally used to view retinal details mainly of the posterior pole during the diagnosis or after treatment.
- In cases of pigmented choroidal lesions when a diagnosis of choroidal melanoma is in question, OCT helps to document subretinal fluid which might be missed clinically, detection of which aids in the diagnosis of such lesions.
- Small lesions less than 1mm are better studied by OCT and Enhanced Depth Imaging(EDI) OCT.
- Macular changes are better appreciated especially radiation maculopathy, where OCT may help in the decision-making for treatment.
- In retinal vascular tumors like choroidal hemangioma OCT detects schisis, subretinal fluid early.
- Suspicious choroidal lesions can be followed up by OCT to determine their growth.
6. Fundus Fluorescein Angiography ( FFA), Indocyanine Green Angiography (ICG)
- FFA is generally not used for diagnosis of intraocular tumours, its general purpose is to rule out simulatings lesions .
- Historically ' double circulation' on FFA has been associated with choroidal melanoma.
- Circulatory features on ICG have been shown to prognosticate choroidal melanoma, with features like 'loops' having a poor prognosis (ref).
- Choroidal hemangioma has a unique ICG pattern: they have early hyperfluorescence which typically shows a 'wash out' phenomenon during the late stages.
Transillumination is useful in pigmented tumors in assessing the margins. It is a useful method of localizing tumor margins during plaque placement. Its usefulness decreases in the pigmented fundus (an inhibiting factor in dark-complexioned persons).
a) Transpupillary: when the light source is placed over the cornea.
b) Transocular: when the light source is placed over the globe opposite to the tumour.
c) Transscleral: when the light source is placed under the tumour to determine its transillumination property.
8. Fine Needle Aspiration Biopsy (FNAB)
- It is generally employed in assessing a lesion's malignant potential when the diagnosis is uncertain.
- FNAB is generally used in pigmented iris, ciliary body, or choroidal lesions to rule out melanoma. It is also useful in various other iris lesions when the diagnosis is in question.
- It is also useful in cases of intraocular lymphoma.
- It can be done through pars plana or the limbal route.
- FNAB can yield poor results due to sampling error, or dry tap.
- Complications like retinal detachment or vision-threatening vitreous hemorrhage are rare although reported.
9. Neuroimaging ( CT, MRI, PET)[1,2]
- CT is commonly employed in developing nations in cases of retinoblastoma to rule out extraocular spread. CT not only increases the exposure to radiation in children in such pathology but also is less sensitive.
- MRI is a better modality in assessing any extraocular spread.
- Choroidal melanoma is hyperintense on T1 and hypointense on T2 MRI. This feature is not diagnostic of melanoma, although it can be a feature to rule out other lesions.
- In cases of ocular lymphoma, neuroimaging is an important investigation to rule out concurrent central nervous system involvement
- In eyes with extensive vitreous hemorrhage when the possibility of malignancy cannot be ruled out MRI is an important investigation.
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2) Damato BE. Ocular Tumours. Diagnosis and treatment. Butterworth-Heinemann 2000
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