diff --git a/exp/lighthorizon/archive/main.go b/exp/lighthorizon/archive/main.go
index e3d7063df5..00b3a57620 100644
--- a/exp/lighthorizon/archive/main.go
+++ b/exp/lighthorizon/archive/main.go
@@ -30,9 +30,39 @@ type LedgerTransactionReader interface {
 
 // Archive here only has the methods LightHorizon cares about, to make caching/wrapping easier
 type Archive interface {
+
+	//GetLedger - retreive a ledger's meta data
+	//
+	//ctx               - the caller's request context
+	//ledgerCloseMeta   - the sequence number of ledger to fetch
+	//
+	//returns error or meta data for requested ledger
 	GetLedger(ctx context.Context, sequence uint32) (xdr.LedgerCloseMeta, error)
+
+	// Close - releases any resources used for this archive instance.
 	Close() error
+
+	// NewLedgerTransactionReaderFromLedgerCloseMeta - get a reader for ledger meta data
+	//
+	// networkPassphrase - the network passphrase
+	// ledgerCloseMeta   - the meta data for a ledger
+	//
+	// returns error or LedgerTransactionReader
 	NewLedgerTransactionReaderFromLedgerCloseMeta(networkPassphrase string, ledgerCloseMeta xdr.LedgerCloseMeta) (LedgerTransactionReader, error)
+
+	// GetTransactionParticipants - get set of all participants(accounts) in a transaction
+	//
+	// transaction - the ledger transaction
+	//
+	// returns error or map with keys of participant account id's and value of empty struct
 	GetTransactionParticipants(transaction LedgerTransaction) (map[string]struct{}, error)
+
+	// GetOperationParticipants - get set of all participants(accounts) in a operation
+	//
+	// transaction - the ledger transaction
+	// operation   - the operation within this transaction
+	// opIndex     - the 0 based index of the operation within the transaction
+	//
+	// returns error or map with keys of participant account id's and value of empty struct
 	GetOperationParticipants(transaction LedgerTransaction, operation xdr.Operation, opIndex int) (map[string]struct{}, error)
 }
diff --git a/exp/lighthorizon/index/modules.go b/exp/lighthorizon/index/modules.go
index ca4c4c6681..9250125ab9 100644
--- a/exp/lighthorizon/index/modules.go
+++ b/exp/lighthorizon/index/modules.go
@@ -109,6 +109,9 @@ func GetTransactionParticipants(transaction ingest.LedgerTransaction) ([]string,
 	return participantsForOperations(transaction, false)
 }
 
+// transaction - the ledger transaction
+// operation   - the operation within this transaction
+// opIndex     - the 0 based index of the operation within the transaction
 func GetOperationParticipants(transaction ingest.LedgerTransaction, operation xdr.Operation, opIndex int) ([]string, error) {
 	return participantsForOperation(transaction, operation, opIndex, false)
 }
@@ -130,6 +133,9 @@ func participantsForOperations(transaction ingest.LedgerTransaction, onlyPayment
 	return participants, nil
 }
 
+// transaction - the ledger transaction
+// operation   - the operation within this transaction
+// opIndex     - the 0 based index of the operation within the transaction
 func participantsForOperation(transaction ingest.LedgerTransaction, operation xdr.Operation, opIndex int, onlyPayments bool) ([]string, error) {
 	participants := []string{}
 	opSource := operation.SourceAccount
diff --git a/exp/lighthorizon/services/main.go b/exp/lighthorizon/services/main.go
index 3bd16f8c54..27baca1ef7 100644
--- a/exp/lighthorizon/services/main.go
+++ b/exp/lighthorizon/services/main.go
@@ -49,7 +49,7 @@ func (os *OperationsService) GetOperationsByAccount(ctx context.Context, cursor
 	ops := []common.Operation{}
 	opsCallback := func(tx archive.LedgerTransaction, ledgerHeader *xdr.LedgerHeader) (bool, error) {
 		for operationOrder, op := range tx.Envelope.Operations() {
-			opParticipants, opParticipantErr := os.Config.Archive.GetOperationParticipants(tx, op, operationOrder+1)
+			opParticipants, opParticipantErr := os.Config.Archive.GetOperationParticipants(tx, op, operationOrder)
 			if opParticipantErr != nil {
 				return false, opParticipantErr
 			}
@@ -59,7 +59,7 @@ func (os *OperationsService) GetOperationsByAccount(ctx context.Context, cursor
 					TransactionResult:   &tx.Result.Result,
 					LedgerHeader:        ledgerHeader,
 					TxIndex:             int32(tx.Index),
-					OpIndex:             int32(operationOrder + 1),
+					OpIndex:             int32(operationOrder),
 				})
 				if uint64(len(ops)) == limit {
 					return true, nil
@@ -146,12 +146,10 @@ func searchTxByAccount(ctx context.Context, cursor int64, accountId string, conf
 			}
 		}
 		nextCursor := toid.New(int32(nextLedger), 1, 1).ToInt64()
-
 		nextLedger, err = getAccountNextLedgerCursor(accountId, nextCursor, config.IndexStore)
-		if err != nil {
-			if err == io.EOF {
-				return nil
-			}
+		if err == io.EOF {
+			return nil
+		} else if err != nil {
 			return err
 		}
 	}
diff --git a/exp/lighthorizon/services/main_test.go b/exp/lighthorizon/services/main_test.go
index 882372d000..ae402bfcea 100644
--- a/exp/lighthorizon/services/main_test.go
+++ b/exp/lighthorizon/services/main_test.go
@@ -152,13 +152,13 @@ func mockArchiveAndIndex(ctx context.Context, passphrase string) (archive.Archiv
 	mockArchive.On("GetTransactionParticipants", expectedLedger3Transaction1).Return(allParticipants, nil)
 	mockArchive.On("GetTransactionParticipants", expectedLedger3Transaction2).Return(partialParticipants, nil)
 
+	mockArchive.On("GetOperationParticipants", expectedLedger1Transaction1, mock.Anything, int(0)).Return(partialParticipants, nil)
 	mockArchive.On("GetOperationParticipants", expectedLedger1Transaction1, mock.Anything, int(1)).Return(partialParticipants, nil)
-	mockArchive.On("GetOperationParticipants", expectedLedger1Transaction1, mock.Anything, int(2)).Return(partialParticipants, nil)
-	mockArchive.On("GetOperationParticipants", expectedLedger1Transaction2, mock.Anything, int(1)).Return(partialParticipants, nil)
-	mockArchive.On("GetOperationParticipants", expectedLedger2Transaction1, mock.Anything, int(1)).Return(partialParticipants, nil)
-	mockArchive.On("GetOperationParticipants", expectedLedger2Transaction2, mock.Anything, int(1)).Return(allParticipants, nil)
-	mockArchive.On("GetOperationParticipants", expectedLedger3Transaction1, mock.Anything, int(1)).Return(allParticipants, nil)
-	mockArchive.On("GetOperationParticipants", expectedLedger3Transaction2, mock.Anything, int(1)).Return(partialParticipants, nil)
+	mockArchive.On("GetOperationParticipants", expectedLedger1Transaction2, mock.Anything, int(0)).Return(partialParticipants, nil)
+	mockArchive.On("GetOperationParticipants", expectedLedger2Transaction1, mock.Anything, int(0)).Return(partialParticipants, nil)
+	mockArchive.On("GetOperationParticipants", expectedLedger2Transaction2, mock.Anything, int(0)).Return(allParticipants, nil)
+	mockArchive.On("GetOperationParticipants", expectedLedger3Transaction1, mock.Anything, int(0)).Return(allParticipants, nil)
+	mockArchive.On("GetOperationParticipants", expectedLedger3Transaction2, mock.Anything, int(0)).Return(partialParticipants, nil)
 
 	mockReaderLedger1.On("Read").Return(expectedLedger1Transaction1, nil).Once()
 	mockReaderLedger1.On("Read").Return(expectedLedger1Transaction2, nil).Once()